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Segment Information (Details) $ in Millions	3 Months Ended		12 Months Ended
Segment Information (Details) $ in Millions	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information
Number of reportable segments \| segment	4
Number of operating segments \| segment	6
Revenues and segment income by reportable segment
Revenues	$ 6,975.4	$ 5,773.8
Segment income	$ 497.6	247.6
Operating segments
Segment Reporting Information
Number of reportable segments \| segment	1
Intersegment Elimination
Revenues and segment income by reportable segment
Revenues	$ 0.0	0.0
Segment income	0.0	0.0
Retail automotive dealership
Revenues and segment income by reportable segment
Revenues	6,029.2	5,206.9	$ 22,500.0
Retail automotive dealership \| Operating segments
Revenues and segment income by reportable segment
Revenues	6,029.2	5,206.9
Segment income	309.9	160.3
Retail commercial truck dealership
Revenues and segment income by reportable segment
Revenues	792.3	434.7
Retail commercial truck dealership \| Operating segments
Revenues and segment income by reportable segment
Revenues	792.3	434.7
Segment income	58.5	27.5
Other \| Operating segments
Revenues and segment income by reportable segment
Revenues	153.9	132.2
Segment income	10.5	6.0
Non-Automotive Investments \| Operating segments
Revenues and segment income by reportable segment
Revenues	0.0	0.0
Segment income	$ 118.7	$ 53.8